Method and device for attenuating the effects of turbulence on an aircraft
A method for attenuating effects of turbulence on an aircraft, and a device to implement the method, the method including: using at least one signal on a wind profile signal, along an excitation direction, representing, at a given moment in an aircraft referential, a component along the excitation direction of the wind speed at a front of the aircraft according to a distance along a longitudinal direction of the aircraft; carrying out a frequency determination, in which the wind profile signal is processed to determine a frequential content; and selecting a control strategy to be adopted according to the previously determined frequential content, the strategy enabling at least one applicable control law to be identified.
1. A method for attenuating effects of turbulence on an aircraft, comprising:
using at least one signal, as a wind profile signal in an excitation direction, representing, at a given instant in an aircraft frame of reference, a component, in the excitation direction, of wind speed ahead of the aircraft according to a plurality of distance points in a longitudinal direction of the aircraft;
executing frequency determination, in which the wind profile signal is processed so as to determine frequency content thereof, the frequency content at the plurality of distance points in the longitudinal direction of the aircraft being representative of the frequency at which the aircraft will be excited in the excitation direction when the aircraft arrives at a position located at the plurality of distance points in the longitudinal direction of the aircraft; and
selecting a control strategy to be adopted according to the determined frequency content, which strategy enables identification of one or more applicable control rules.
2. A method according to claim 1 , wherein a control rule to be applied to operate mobile control surfaces of the aircraft is chosen according to the selected control strategy and one or more amplitude maxima presented by the wind profile signal.
3. A method according to claim 2 , wherein an entirety of the control rule to be applied is determined by taking into account a phase difference that may exist between actuation of each mobile control surface affected by the control rule and a corresponding response of the aircraft.
4. A method according to claim 1 , wherein, in the executing a frequency-determination, the wind profile signal is processed so as to determine if the wind profile signal or part thereof contains at least one frequency included in at least one predefined frequency range.
5. A method according to claim 4 , wherein the wind profile signal is processed so as to determine if the wind profile signal or part thereof contains at least one frequency close to a rigid natural mode of the aircraft.
6. A method according to claim 5 , wherein the processed signal is a wind profile signal in the vertical direction and the signal is processed so as to determine if the wind profile signal or part thereof contains at least one frequency close to an incidence oscillation frequency of the aircraft.
7. A method according to claim 6 , wherein the wind profile signal is processed so as to determine if the wind profile signal contains at least one frequency lower than 0.5 Hz.
8. A method according to claim 4 , wherein the wind profile signal is processed so as to determine if the wind profile signal or part thereof contains at least one frequency close to a flexible natural mode of the aircraft.
9. A method according to claim 8 , wherein the processed signal is a wind profile signal in the vertical direction, and the signal is processed so as to determine if a part thereof corresponding to a distance range [0; 400 m] or [0; 2 s] contains at least one frequency above 0.5 Hz, or if a part thereof corresponding to the distance range [0; 200 m] or [0; 1 s] contains at least one frequency higher than or equal to 1 Hz.
10. A method according to claim 4 , wherein, in the selecting the control strategy:
if the determined frequency content is composed mainly of frequencies close to a rigid natural mode of the aircraft, a control comfort strategy is selected, intended to improve comfort of persons in the aircraft,
if the determined frequency content is composed mainly of frequencies close to a flexible natural mode of the aircraft, a control structural preservation strategy is selected, intended to preserve a structure of the aircraft, and
if the determined frequency content is composed both of frequencies close to a rigid natural mode of the aircraft and of frequencies close to a flexible natural mode thereof, in substantially equivalent proportions, a control mixed strategy is selected, intended to simultaneously improve the comfort of persons and to preserve the structure of the aircraft.
11. A method according to claim 10 , wherein:
the selection of the comfort strategy leads to application of control rules that bring about activation of mobile control surfaces chosen from among: elevators, rudders, elevons, flaperons, spoilers, ailerons, and
the selection of the structural preservation strategy leads to application of control rules that bring about activation of mobile control surfaces chosen from among: ailerons, spoilers, flaps, slats, elevators, rudders.
12. A method according to claim 1 , wherein the wind profile signal represents the wind speed ahead of the aircraft at various distances.
13. A device for attenuating effects of turbulence on an aircraft, comprising:
frequency-determining means, configured to process a wind profile signal in a excitation direction, so as to determine frequency content thereof, which signal represents, at a given instant in an aircraft frame of reference, a component, in the excitation direction, of wind speed ahead of the aircraft according to a plurality of distance points in a longitudinal direction of the aircraft, the frequency content at the plurality of distance points in the longitudinal direction of the aircraft being representative of the frequency at which the aircraft will be excited in the excitation direction when the aircraft arrives at a position located at the plurality of distance points in the longitudinal direction of the aircraft; and
means for selecting a control strategy to be adopted according to the determined frequency content, which strategy makes it possible to identify one or more applicable control rules.
14. A device according to claim 13 , further comprising means for determining a control rule to be applied to operate mobile control surfaces of the aircraft, configured to determine an entirety of the control rule by taking into account a phase difference that may exist between actuation of each mobile control surface in question and a corresponding response of the aircraft.
15. An aircraft, comprising a device for attenuating effects of turbulence on the aircraft, configured to employ a method according to claim 1 .